Heterometallic FeIII-CeIV complexes from the use of aliphatic aminoalcohol ligands

Abstract

Six novel heteronuclear FeIII/CeIV clusters with the ligands 3-amino-1-propanol (Hap) and 2-(hydroxymethyl)piperidine (Hhmpip) [FeIII4CeIV6O8(L) 4((CH3)3CCO2)12(RCO 2)4] (R = CH3, L = ap-, 1

R = ClCH2, L = ap-, 2

R = BrCH2, L = ap -, 3

R = C2H5, L = ap-, 4

R = CH3, L = hmpip-, 5) and ([Fe2Ce 2Na2O2((CH3)3CCO 2)8(N3)2(ap)2]) ∞ (6)∞ are reported. Compounds 1-5 were prepared from reactions of preformed trinuclear Fe3+ clusters with the ligands, in the presence of (NH4)2Ce(NO 3)6 and RCO2M (R = CH3, M + = H+, 1

R = ClCH2, M+ = Na +, 2

R = BrCH2, M+ = Na+, 3

R = CH3CH2, M+ = Na+, 4

R = CH 3, M+ = H+, 5) in 1:5:1:1 molar ratio in CH3CN. Complex (6·2CH3CN)∞ was prepared by a similar to the above described synthetic procedure that involved the use of NaN3 instead of RCO2M. To the best of our knowledge, compounds 1-6 are the initial examples of FeIII/Ce IV species and rare examples of metal complexes with the ligands Hap and Hhmpip. The structures of 1-5 are composed of a distorted supertetrahedral [FeIII4CeIV6(μ4-O) 4(μ3-O)4]20+ structural core, while (6·2CH3CN)∞ displays a [Fe III2CeIV2Na2(μ 4-O)2]12+ core consisting of two tetrahedral units sharing one common edge. These two structural types are rather uncommon for mixed metal 3d/4f compounds although they are well-known for 3d metal cluster chemistry. Variable temperature dc magnetic susceptibility studies on powdered microcrystalline samples of 1 and (6·2CH3CN) ∞ revealed the presence of weak antiferromagnetic interactions as expected on the basis of the large separations (>6 Å) between the paramagnetic Fe3+ ions in both complexes.